NCERT-Class-10-Science-Exemplar-Problems ( PDFDrive )

5CHAPTER Periodic Classification of Elements Multiple Choice Q uestions 1. Upto which element, the Law of Octaves was found to be applicable (a) Oxygen (b) Calcium (c) Cobalt (d) Potassium 2 . According to ▼❡♥❞❡ ❡✂ ❡✈✁s Periodic Law, the elements were arranged in the periodic table in the order of (a) increasing atomic number (b) decreasing atomic number (c) increasing atomic masses (d) decreasing atomic masses 3. In ▼❡♥❞❡ ❡✂ ❡✈ ’s Periodic Table, gaps were left for the elements to be discovered later. Which of the following elements found a place in the perioidc table later (a) Germanium (b) Chlorine (c) Oxygen (d) Silicon 4. Which of the following statement (s) about the Modern Periodic Table are incorrect (i) The elements in the Modern Periodic Table are arranged on the basis of their decreasing atomic number (ii) The elements in the Modern Periodic Table are arranged on the basis of their increasing atomic masses (iii) Isotopes are placed in adjoining group (s) in the Periodic Table (iv) The elements in the Modern Periodic Table are arranged on the basis of their increasing atomic number (a) (i) only (b) (i), (ii) and (iii) (c) (i), (ii) and (iv) (d) (iv) only

5. Which of the following statements about the Modern Periodic Table 39 is correct: (a) It has 18 horizontal rows known as Periods (b) It has 7 vertical columns known as Periods (c) It has 18 vertical columns known as Groups (d) It has 7 horizontal rows known as Groups 6. Which of the given elements A, B, C, D and E with atomic number 2, 3, 7, 10 and 30 respectively belong to the same period? (a) A, B, C (b) B, C, D (c) A, D, E (d) B, D, E 7. The elements A, B, C, D and E have atomic number 9, 11, 17, 12 and 13 respectively. Which pair of elements belong to the same grou p? (a) A and B (b) B and D (c) A and C (d) D and E 8. Where would you locate the element with electronic configuration 2,8 in the Modern Periodic Table? (a) Group 8 (b) Group 2 (c) Group 18 (d) Group 10 9. An element which is an essential constituent of all organic compounds belongs to (a) group 1 (b) group 14 (c) group 15 (d) group 16 10. Which of the following is the outermost shell for elements of period 2? (a) K shell (b) L shell (c) M shell (d) N shell PERIODIC C LASSIFICATION OF ELEMENTS

11. Which one of the following elements exhibit maximum number of valence electrons? (a) Na (b) Al (c) Si (d) P 12. Which of the following gives the correct increasing order of the atomic radii of O, F and N ? (a) O, F, N (b) N, F, O (c) O, N, F (d) F, O, N 13. Which among the following elements has the largest atomic radii? (a) Na (b) Mg (c) K (d) Ca 14. Which of the following elements would lose an electron easily? (a) Mg (b) Na (c) K (d) Ca 15. Which of the following elements does not lose an electron easily? (a) Na (b) F (c) Mg (d) Al 16. Which of the following are the characteristics of isotopes of an element? (i) Isotopes of an element have same atomic masses (ii) Isotopes of an element have same atomic number (iii) Isotopes of an element show same physical properties (iv) Isotopes of an element show same chemical properties (a) (i), (iii) and (iv) (b) (ii), (iii) and (iv) (c) (ii) and (iii) (d) (ii) and (iv) 40 EXE M PLAR P RO B LE M S – SCIENCE

17. Arrange the following elements in the order of their decreasing 41 metallic character Na, Si, Cl, Mg, Al (a) Cl > Si >Al > Mg >Na (b) Na >Mg >Al >Si > Cl (c) Na > Al > Mg > Cl > Si (d) Al > Na> Si > Ca> Mg 18. Arrange the following elements in the order of their increasing non- metallic character Li, O, C, Be, F (a) F < O < C < Be < Li (b) Li < Be < C < O< F (c) F < O < C < Be < Li (d) F < O < Be < C < Li 19. What type of oxide would Eka– aluminium form? (a) EO 3 (b) E3 O 2 (c) E2 O3 (d) EO 20. Three elements B, Si and Ge are (a) metals (b) non-metals (c) metalloids (d) metal, non-metal and metalloid respectively 21. Which of the following elements will form an acidic oxide? (a) An element with atomic number 7 (b) An element with atomic number 3 (c) An element with atomic number 12 (d) An element with atomic number 19 22. The element with atomic number 14 is hard and forms acidic oxide and a covalent halide. To which of the following categories does the element belong? (a) Metal (b) Metalloid (c) Non-metal (d) Left-hand side element PERIODIC C LASSIFICATION OF ELEMENTS

23. Which one of the following depict the correct representation of atomic radius(r) of an atom? (i) (ii) (iii) (iv) (a) (i) and (ii) (b) (ii) and (iii) (c) (iii) and (iv) (d) (i) and (iv) 24. Which one of the following does not increase while moving down the group of the periodic table? (a) Atomic radius (b) Metallic character (c) Valence (d) Number of shells in an element 25. On moving from left to right in a period in the periodic table, the size of the atom. (a) increases (b) decreases (c) does not change appreciably (d) first decreases and then increases 42 EXE M PLAR P RO B LE M S – SCIENCE

26. Which of the following set of elements is written in order of their increasing metallic character? (a) Be Mg Ca (b) Na Li K (c) Mg Al Si (d) C O N Short Answer Q uestions 27. The three elements A, B and C with similar properties have atomic masses X, Y and Z respectively. The mass of Y is approximately equal to the average mass of X and Z. What is such an arrangement of elements called as? Give one example of such a set of elements. 28. Elements have been arranged in the following sequence on the basis of their increasing atomic masses. F, Na, Mg, Al, Si, P, S, Cl, Ar, K (a) Pick two sets of elements which have similar properties. (b) The given sequence represents which law of classification of elements? 29. Can the following groups of elements be classified as ❉✁ ✁❜❡r❡✐♥❡r✬s triad ? (a) Na, Si, Cl (b) Be, Mg, Ca Atomic mass of Be 9; Na 23; Mg 24; Si 28; Cl 35; Ca 40 Explain by giving reason. 30. In ▼✂✄❞✂❧✂☎ ✂✈ ’s Periodic Table the elements were arranged in the increasing order of their atomic masses. However, cobalt with atomic mass of 58.93 amu was placed before nickel having an atomic mass of 58.71 amu. Give reason for the same. 31. “Hydrogen occupies a unique position in Modern Periodic Table”. Justify the statement. 32. Write the formulae of chlorides of Eka-silicon and Eka-aluminium, the elements predicted by ▼✂✄❞✂❧✂☎ ✂✈✳ 33. Three elements A, B and C have 3, 4 and 2 electrons respectively in their outermost shell. Give the group number to which they belong in the Modern Periodic Table. Also, give their valencies. PERIODIC C LASSIFICATION OF ELEMENTS 43

34. If an element X is placed in group 14, what will be the formula and the nature of bonding of its chloride? 35. Compare the radii of two species X and Y. Give reasons for your answer. (a) X has 12 protons and 12 electrons (b) Y has 12 protons and 10 electrons 36. Arrange the following elements in increasing order of their atomic radii. (a) Li, Be, F, N (b) Cl, At, Br I 37. Identify and name the metals out of the following elements whose electronic configurations are given below. (a) 2, 8, 2 (b) 2, 8, 1 (c) 2, 8, 7 (d) 2, 1 38. Write the formula of the product formed when the element A (atomic number 19) combines with the element B (atomic number 17). Draw its electronic dot structure. What is the nature of the bond formed? 39. Arrange the following elements in the increasing order of their metallic character Mg, Ca, K, Ge, Ga 40. Identify the elements with the following property and arrange them in increasing order of their reactivity (a) An element which is a soft and reactive metal (b) The metal which is an important constituent of limestone (c) The metal which exists in liquid state at room temperature 41. Properties of the elements are given below. Where would you locate the following elements in the periodic table? (a) A soft metal stored under kerosene (b) An element with variable (more than one) valency stored under water. (c) An element which is tetravalent and forms the basis of organic chemistry (d) An element which is an inert gas with atomic number 2 (e) An element whose thin oxide layer is used to make other elements corrosion resistant by the process of “ anodising” 44 EXE M PLAR P RO B LE M S – SCIENCE

Long Answer Q uestions 42. An element is placed in 2nd Group and 3rd Period of the Periodic Table, burns in presence of oxygen to form a basic oxide. (a) Identify the element (b) Write the electronic configuration (c) Write the balanced equation when it burns in the presence of air (d) Write a balanced equation when this oxide is dissolved in water (e) Draw the electron dot structure for the formation of this oxide 43. An element X (atomic number 17) reacts with an element Y (atomic number 20) to form a divalent halide. (a) Where in the periodic table are elements X and Y placed? (b) Classify X and Y as metal (s), non-metal (s) or metalloid (s) (c) What will be the nature of oxide of element Y? Identify the nature of bonding in the compound formed (d) Draw the electron dot structure of the divalent halide 44. Atomic number of a few elements are given below 10, 20, 7, 14 (a) Identify the elements (b) Identify the Group number of these elements in thePeriodic Table (c) Identify the Periods of these elements in the Periodic Table (d) What would be the electronic configuration for each of these elements? (e) Determine the valency of these elements 45. Complete the following cross word puzzle (Figure 5.1) Across: Fig. 5.1 (1) An element with atomic number 12. (3) Metal used in making cans and member of Group 14. (4) A lustrous non-metal which has 7 electrons in its outermost shell. Down: (2) Highly reactive and soft metal which imparts yellow colou r when subjected to flame and is kept in kerosene. PERIODIC C LASSIFICATION OF ELEMENTS 45

(5) The first element of second Period (6) An element which is used in making fluorescent bulbs and is second member of Group 18 in the Modern Periodic Table (7) A radioactive element which is the last member of halogen family. (8) Metal which is an important constituent of steel and forms rust when exposed to moist air. (9) The first metalloid in Modern Periodic Table whose fibres are used in making bullet-proof vests 46. (a) In this ladder (Figure 5.2) symbols of elements are jumbled up. Rearrange these symbols of elements in the increasing order of their atomic number in the Periodic Table. (b) Arrange them in the order of their group also. Fig. 5.2 47. ▼❡♥❞❡ ❡✁ ❡✈ predicted the existence of certain elements not known at that time and named two of them as Eka-silicon and Eka-aluminium. (a) Name the elements which have taken the place of these elements (b) Mention the group and the period of these elements in the Modern Periodic Table. (c) Classify these elements as metals, non-metals or metalloids (d) How many valence electrons are present in each one of them? 48. (a) Electropositive nature of the element(s) increases down the group and decreases across the period (b) Electronegativity of the element decreases down the group and increases across the period (c) Atomic size increases down the group and decreases across a period (left to right) (d) Metallic character increases down the group and decreases across a period. 46 EXE M PLAR P RO B LE M S – SCIENCE

On the basis of the above trends of the Periodic Table, answer the following about the elements with atomic numbers 3 to 9. (a) Name the most electropositive element among them (b) Name the most electronegative element (c) Name the element with smallest atomic size (d) Name the element which is a metalloid (e) Name the element which shows maximum valency. 49. An element X which is a yellow solid at room temperature shows catenation and allotropy. X forms two oxides which are also formed during the thermal decomposition of ferrous sulphate crystals and are the major air pollutants. (a) Identify the element X (b) Write the electronic configuration of X (c) W rite the balanced chemical equation for the thermal decomposition of ferrous sulphate crystals? (d) What would be the nature (acidic/ basic) of oxides formed? (e) Locate the position of the element in the Modern Periodic Table. 50. An element X of group 15 exists as diatomic molecule and combines with hydrogen at 773 K in presence of the catalyst to form a compound, ammonia which has a characteristic pungent smell. (a) Identify the element X. How many valence electrons does it have? (b) Draw the electron dot structure of the diatomic molecule of X. What type of bond is formed in it? (c) Draw the electron dot structure for ammonia and what type of bond is formed in it? 51. Which group of elements could be placed in ▼❡♥❞❡ ❡✂ ❡✈✁s Periodic Table without disturbing the original order? Give reason. 52. Give an account of the process adopted by ▼❡♥❞❡ ❡✂ ❡✈ for the classification of elements. How did he arrive at “Periodic Law”? PERIODIC C LASSIFICATION OF ELEMENTS 47

6CHAPTER Life Processes Multiple Choice Q uestions 1. Which of the following statements about the autotrophs is incorrect? (a) They synthesise carbohydrates from carbon dioxide and water in the presence of sunlight and chlorophyll (b) They store carbohydrates in the form of starch (c) They convert carbon dioxide and water into carbohydrates in the absence of sunlight (d) They constitute the first trophic level in food chains 2. In which of the following groups of organisms, food material is broken down outside the body and absorbed? (a) Mushroom, green plants, Amoeba (b) Yeast, mushroom, bread mould (c) Paramecium, Amoeba, Cuscuta (d) Cuscuta, lice, tapeworm 3. Select the correct statement (a) Heterotrophs do not synthesise their own food (b) Heterotrophs utilise solar energy for photosynthesis (c) Heterotrophs synthesise their own food (d) Heterotrophs are capable of converting carbon dioxide and water into carbohydrates 4. Which is the correct sequence of parts in human alimentary canal? ✂ ✂ ✂(a) Mouth stomach small intestine oesophagus ✂ large intestine ✂ ✂ ✂(b) Mouth oesophagus stomach large intestine ✂ small intestine ✂ ✂ ✂(c) Mouth stomach oesophagus small intestine ✂ large intestine ✂ ✂ ✂(d) Mouth oesophagus ✂ large intestine stomach small intestine

5. If salivary amylase is lacking in the saliva, which of the following 49 events in the mouth cavity will be affected? (a) Proteins breaking down into amino acids (b) Starch breaking down into sugars (c) Fats breaking down into fatty acids and glycerol (d) Absorption of vitamins 6. The inner lining of stomach is protected by one of the following from hydrochloric acid. Choose the correct one (a) Pepsin (b) Mucus (c) Salivary amylase (d) Bile 7. Which part of alimentary canal receives bile from the liver? (a) Stomach (b) Small intestine (c) Large intestine (d) Oesophagus 8. A few drops of iodine solution were added to rice water. The solution turned blue-black in colour. This indicates that rice water contains (a) complex proteins (b) simple proteins (c) fats (d) starch 9. In which part of the alimentary canal food is finally digested? (a) Stomach (b) Mouth cavity (c) Large intestine (d) Small intestine 10. Choose the function of the pancreatic juice from the following (a) trypsin digests proteins and lipase carbohydrates (b) trypsin digests emulsified fats and lipase proteins (c) trypsin and lipase digest fats (d) trypsin digests proteins and lipase emulsified fats 11. When air is blown from mouth into a test-tube containing lime water, the lime water turned milky due to the presence of (a) oxygen (b) carbon dioxide (c) nitrogen (d) water vapour LIFE PROCESSES

12. The correct sequence of anaerobic reactions in yeast is (a) Glucose Pyruvate Ethanol (b) Glucose Pyruvate + Carbondioxide Lactic acid (c) Glucose Pyruvate Lactic acid (d) Glucose Pyruvate Ethanol + Carbondioxide 13. Which of the following is most appropriate for aerobic respiration? (a) Glucose Pyruvate CO +H O+ Energy 22 (b) Glucose Pyruvate CO +H O+ Energy (c) Glucose 22 CO +H O Pyruvate + Energy 22 Pyruvate + Energy (d) Glucose CO2+H2O+ Energy 14. Which of the following statement(s) is (are) true about respiration? (i) During inhalation, ribs move inward and diaphragm is raised (ii) In the alveoli, exchange of gases takes place i.e., oxygen from alveolar air diffuses into blood and carbon dioxide from blood into alveolar air (iii) Haemoglobin has greater affinity for carbon dioxide than oxygen (iv) Alveoli increase surface area for exchange of gases (a) (i) and (iv) (b) (ii) and (iii) (c) (i) and (iii) (d) (ii) and (iv) 15. Which is the correct sequence of air passage during inhalation? ✂ ✂ ✂ ✂(a) Nostrils larynx pharynx trachea lungs ✂ ✂ ✂ ✂(b) Nasal passage trachea pharynx larynx alveoli ✂ ✂ ✂(c) larynx nostrils pharynx lungs ✂ ✂ ✂ ✂(d) Nostrils pharynx larynx trachea alveoli 16. During respiration exchange of gases take place in (a) trachea and larynx (b) alveoli of lungs (c) alveoli and throat (d) throat and larynx 50 E XE M PLAR PRO B LE M S – SCIENCE

17. Which of the following statement (s) is (are) true about heart? (i) Left atrium receives oxygenated blood from different parts of body while right atrium receives deoxygenated blood from lungs (ii) Left ventricle pumps oxygenated blood to different body parts while right ventricle pumps deoxygenated blood to lungs (iii) Left atrium transfers oxygenated blood to right ventricle which sends it to different body parts (iv) Right atrium receives deoxygenated blood from different parts of the body while left ventricle pumps oxygenated blood to different parts of the body (a) (i) (b) (ii) (c) (ii) and (iv) (d) (i) and (iii) 18. W hat prevents backflow of blood inside the heart during contraction? (a) Valves in heart (b) Thick muscular walls of ventricles (c) Thin walls of atria (d) All of the above 19. Single circulation i.e., blood flows through the heart only once during one cycle of passage through the body, is exhibited by (a) Labeo, Chameleon, Salamander (b) Hippocampus, Exocoetus, Anabas (c) Hyla, Rana, Draco (d) Whale, Dolphin, Turtle 20. In which of the following vertebrate group/groups, heart does not pump oxygenated blood to different parts of the body? (a) Pisces and amphibians (b) Amphibians and reptiles (c) Amphibians only (d) Pisces only 21. Choose the correct statement that describes arteries. (a) They have thick elastic walls, blood flows under high pressure; collect blood from different organs and bring it back to the heart (b) They have thin walls with valves inside, blood flows under low pressure and carry blood away from the heart to various organs of the body (c) They have thick elastic walls, blood flows under low pressure; carry blood from the heart to various organs of the body (d) They have thick elastic walls without valves inside, blood flows under high pressure and carry blood away from the heart to different parts of the body. LIFE PROCESSES 51

22. The filtration units of kidneys are called (a) ureter (b) urethra (c) neurons (d) nephrons 23. Oxygen liberated during photosynthesis comes from (a) water (b) chlorophyll (c) carbon dioxide (d) glucose 24. The blood leaving the tissues becomes richer in (a) carbon dioxide (b) water (c) heamoglobin (d) oxygen 25. Which of the following is an incorrect statement? (a) Organisms grow with time (b) Organisms must repair and maintain their structure (c) Movement of molecules does not take place among cells (d) Energy is essential for life processes 26. The internal (cellular) energy reserve in autotrophs is (a) glycogen (b) protein (c) starch (d) fatty acid 27. W hich of the following equ ations is the su mmary of photosynthesis? ✂(a) 6CO + 12H O C H O + 6O + 6H O 22 6 12 6 22 ✂(b) 6CO2 + H2O + Sunlight C 6H12O6 + O2+ 6H2O ✂(c) 6CO + 12H O + Chlorophyll + Sunlight C H O + 6O + 6H O ✂2 2 6 12 6 22 (d) 6CO2 + 12H2O + Chlorophyll + Sunlight C6H12O6 + 6CO2+ 6H2O 28. Choose the event that does not occur in photosynthesis (a) Absorption of light energy by chlorophyll (b) Reduction of carbon dioxide to carbohydrates (c) Oxidation of carbon to carbon dioxide (d) Conversion of light energy to chemical energy 52 E XE M PLAR PRO B LE M S – SCIENCE

29. The opening and closing of the stomatal pore depends upon (a) oxygen (b) temperature (c) water in guard cells (d) concentration of CO2 in stomata 30. Choose the forms in which most plants absorb nitrogen (i) Proteins (ii) Nitrates and Nitrites (iii) Urea (iv) Atmospheric nitrogen (a) (i) and (ii) (b) (ii) and (iii) (c) (iii) and (iv) (d) (i) and (iv) 31. Which is the first enzyme to mix with food in the digestive tract? (a) Pepsin (b) Cellulase (c) Amylase (d) Trypsin 32. Which of the following statement(s) is (are) correct? (i) Pyruvate can be converted into ethanol and carbon dioxide by yeast (ii) Fermentation takes place in aerobic bacteria (iii) Fermentation takes place in mitochondria (iv) Fermentation is a form of anaerobic respiration (a) (i) and (iii) (b) (ii) and (iv) (c) (i) and (iv) (d) (ii) and (iii) 33. Lack of oxygen in muscles often leads to cramps among cricketers. This results due to (a) conversion of pyruvate to ethanol (b) conversion of pyruvate to glucose (c) non conversion of glucose to pyruvate (d) conversion of pyruvate to lactic acid 34. Choose the correct path of urine in our body ✂ ✂ ✂(a) kidney ureter urethra urinary bladder ✂ ✂ ✂(b) kidney urinary bladder urethra ureter ✂ ✂ ✂(c) kidney ureters urinary bladder urethra ✂ ✂ ✂(d) urinary bladder kidney ureter urethra LIFE PROCESSES 53

35. During deficiency of oxygen in tissues of human beings, pyruvic acid is converted into lactic acid in the (a) cytoplasm (b) chloroplast (c) mitochondria (d) golgi body Short Answer Q uestions 36. Name the following (a) The process in plants that links light energy with chemical energy (b) Organisms that can prepare their own food (c) The cell organelle where photosynthesis occurs (d) Cells that surround a stomatal pore (e) Organisms that cannot prepare their own food (f) An enzyme secreted from gastric glands in stomach that acts on proteins. 37. “All plants give out oxygen during day and carbon dioxide during night”. Do you agree with this statement? Give reason. 38. How do the guard cells regulate opening and closing of stomatal pores? 39. Two green plants are kept separately in oxygen free containers, one in the dark and the other in continuous light. Which one will live longer? Give reasons. 40. If a plant is releasing carbon dioxide and taking in oxygen during the day, does it mean that there is no photosynthesis occurring? Justify your answer. 41. Why do fishes die when taken out of water? 42. Differentiate between an autotroph and a heterotroph. 43. Is ‘nutrition’ a necessity for an organism? Discuss. 44. What would happen if green plants disappear from earth? 45. Leaves of a healthy potted plant were coated with vaseline. Will this plant remain healthy for long? Give reasons for your answer. 46. How does aerobic respiration differ from anaerobic respiration? 54 E XE M PLAR PRO B LE M S – SCIENCE

47. Match the words of Column (A) with that of Column (B) Column (A) Column (B) (a) Phloem (i) Excretion (b) Nephron (ii) Translocation of food (c) Veins (iii) Clotting of blood (d) Platelets (iv) Deoxygenated blood 48. Differentiate between an artery and a vein. 49. What are the adaptations of leaf for photosynthesis? 50. Why is small intestine in herbivores longer than in carnivores? 51. What will happen if mucus is not secreted by the gastric glands? 52. What is the significance of emulsification of fats? 53. What causes movement of food inside the alimentary canal? 54. Why does absorption of digested food occur mainly in the small intestine? 55. Match Group (A) with Group (B) Group (A) Group (B) (a) Autotrophic nutrition (i) Leech (b) Heterotrophic nutrition (ii) Paramecium (c) Parasitic nutrition (iii) Deer (d) Digestion in food vacuoles (iv) Green plant 56. Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms? 57. Why is blood circulation in human heart called double circulation? 58. What is the advantage of having four chambered heart? 59. Mention the major events during photosynthesis 60. In each of the following situations what happens to the rate of photosynthesis? (a) Cloudy days (b) No rainfall in the area (c) Good manuring in the area (d) Stomata get blocked due to dust 61. Name the energy currency in the living organisms. When and where is it produced? LIFE PROCESSES 55

62. What is common for cuscuta, ticks and leeches? 63. Explain the role of mouth in digestion of food. 64. What are the functions of gastric glands present in the wall of the stomach? 65. Match the terms in Column (A) with those in Column (B) Column (A) Group (B) (a) Trypsin (i) Pancreas (b) Amylase (ii) Liver (c) Bile (iii) Gastric glands (d) Pepsin (iv) Saliva 66. Name the correct substrates for the following enzymes (a) Trypsin (b) Amylase (c) Pepsin (d) Lipase 67. Why do veins have thin walls as compared to arteries? 68. What will happen if platelets were absent in the blood? 69. Plants have low energy needs as compared to animals. Explain. 70. Why and how does water enter continuously into the root xylem? 71. Why is transpiration important for plants? 72. How do leaves of plants help in excretion? Long Answer Q uestions 73. Explain the process of nutrition in Amoeba. 74. Describe the alimentary canal of man. 75. Explain the process of breathing in man. 76. Explain the importance of soil for plant growth. 77. Draw the diagram of alimentary canal of man and label the following parts. Mouth, Oesophagus, Stomach, Intestine 78. How do carbohydrates, proteins and fats get digested in human beings? 79. Explain the mechanism of photosynthesis. 80. Explain the three pathways of breakdown in living organisms. 81. Describe the flow of blood through the heart of human beings. 82. Describe the process of urine formation in kidneys. 56 E XE M PLAR PRO B LE M S – SCIENCE

7CHAPTER Control and Coordination Multiple Choice Q uestions 1. Which of the following statements is correct about receptors? (a) Gustatory receptors detect taste while olfactory receptors detect smell (b) Both gustatory and olfactory receptors detect smell (c) Auditory receptors detect smell and olfactory receptors detect taste (d) Olfactory receptors detect taste and gustatory receptors smell 2. Electrical impulse travels in a neuron from ✥ ✥ ✥(a) Dendrite axon axonal end cell body ✥ ✥ ✥(b) Cell body dendrite axon axonal end ✥ ✥ ✥(c) Dendrite cell body axon axonal end ✥ ✥ ✥(d) Axonal end axon cell body dendrite 3. In a synapse, chemical signal is transmitted from (a) dendritic end of one neuron to axonal end of another neuron (b) axon to cell body of the same neuron (c) cell body to axonal end of the same neuron (d) axonal end of one neuron to dendritic end of another neuron 4. In a neuron, conversion of electrical signal to a chemical signal occurs at/in (a) cell body (b) axonal end (c) dendritic end (d) axon 5. Which is the correct sequence of the components of a reflex arc? ✥ ✥ ✥ ✥(a) Receptors Muscles Sensory neuron Motor neuron Spinal cord ✥ ✥ ✥ ✥(b) Receptors Motor neuron Spinal cord Sensory neuron Muscle ✥ ✥ ✥ ✥(c) Receptors Spinal cord Sensory neuron Motor neuron Muscle ✥ ✥ ✥ ✥(d) Receptors Sensory neuron Spinal cord Motor neuron Muscle

6. Which of the following statements are true? (i) Sudden action in response to something in the environment is called reflex action (ii) Sensory neurons carry signals from spinal cord to muscles (iii) Motor neurons carry signals from receptors to spinal cord (iv) The path through which signals are transmitted from a receptor to a muscle or a gland is called reflex arc (a) (i) and (ii) (b) (i) and (iii) (c) (i) and (iv) (d) (i) , (ii) and (iii) 7. Which of the following statements are true about the brain? (i) The main thinking part of brain is hind brain (ii) Centres of hearing, smell, memory, sight etc are located in fore brain. (iii) Involuntary actions like salivation, vomiting, blood pressure are controlled by the medulla in the hind brain (iv) Cerebellum does not control posture and balance of the body (a) (i) and (ii) (b) (i), (ii) and (iii) (c) (ii) and (iii) (d) (iii) and (iv) 8. Posture and balance of the body is controlled by (a) cerebrum (b) cerebellum (c) medulla (d) pons 9. Spinal cord originates from (a) cerebrum (b) medulla (c) pons (d) cerebellum 10. The movement of shoot towards light is (a) geotropism (b) hydrotropism (c) chemotropism (d) phototropism 11. The main function of abscisic acid in plants is to (a) increase the length of cells (b) promote cell division (c) inhibit growth (d) promote growth of stem 58 EXE M PLAR P RO B LE M S – SCIENCE

12. Which of the following is not associated with growth of plant? 59 (a) Auxin (b) Gibberellins (c) Cytokinins (d) Abscisic acid 13. Iodine is necessary for the synthesis of which hormone? (a) Adrenaline (b) Thyroxin (c) Auxin (d) Insulin 14. Choose the incorrect statement about insulin (a) It is produced from pancreas (b) It regulates growth and development of the body (c) It regulates blood sugar level (d) Insufficient secretion of insulin will cause diabetes 15. Select the mis-matched pair (a) Adrenaline : Pituitary gland (b) Testosterone: Testes (c) Estrogen : Ovary (d) Thyroxin : Thyroid gland 16. The shape of guard cells changes due to change in the (a) protein composition of cells (b) temperature of cells (c) amount of water in cells (d) position of nucleus in the cells 17. The growth of tendril in pea plants is due to (a) effect of light (b) effect of gravity (c) rapid cell divisions in tendrillar cells that are away from the support (d) rapid cell divisions in tendrillar cells in contact with the support 18. The growth of pollen tubes towards ovules is due to (a) hydrotropism (b) chemotropism (c) geotropism (d) phototropism CONTROL AND CO - ORDINATION

19. The movement of sunflower in accordance with the path of sun is due to (a) phototropism (b) geotropism (c) chemotropism (d) hydrotropism 20. The substance that triggers the fall of mature leaves and fruits from plants is due to (a) auxin (b) gibberellin (c) abscisic acid (d) cytokinin 21. Which of the following statements about transmission of nerve impulse is incorrect? (a) Nerve impulse travels from dendritic end towards axonal end (b) At the dendritic end electrical impulses bring about the release of some chemicals which generate an electrical impulse at the axonal end of another neuron (c) The chemicals released from the axonal end of one neuron cross the synapse and generate a similar electrical impulse in a dendrite of another neuron (d) A neuron transmits electrical impulses not only to another neuron but also to muscle and gland cells 22. Involuntary actions in the body are controlled by (a) medulla in fore brain (b) medulla in mid brain (c) medulla in hind brain (d) medulla in spinal cord 23. Which of the following is not an involuntary action? (a) Vomiting (b) Salivation (c) Heart beat (d) Chewing 24. When a person is suffering from severe cold, he or she cannot (a) differentiate the taste of an apple from that of an ice cream (b) differentiate the smell of a perfume from that of an agarbatti (c) differentiate red light from green light (d) differentiate a hot object from a cold object 60 EXE M PLAR P RO B LE M S – SCIENCE

25. What is the correct direction of flow of electrical impulses? 61 (a) (b) (c) (d) Fig. 7.1 26. Which statement is not true about thyroxin? (a) Iron is essential for the synthesis of thyroxin (b) It regulates carbohydrates, protein and fat metabolism in the body (c) Thyroid gland requires iodine to synthesise thyroxin (d) Thyroxin is also called thyroid hormone 27. Dwarfism results due to (a) Excess secretion of thyroxin (b) Less secretion of growth hormone (c) Less secretion of adrenaline (d) Excess secretion of growth hormone 28. Dramatic changes of body features associated with puberty are mainly because of secretion of (a) oestrogen from testes and testosterone from ovary (b) estrogen from adrenal gland and testosterone from pituitary gland (c) testosterone from testes and estrogen from ovary (d) testosterone from thyroid gland and estrogen from pituitary gland 29. A doctor advised a person to take an injection of insulin because (a) his blood pressure was low (b) his heart was beating slowly (c) he was suffering from goitre (d) his sugar level in blood was high CONTROL AND CO - ORDINATION

30. The hormone which increases the fertility in males is called (a) oestrogen (b) testosterone (c) insulin (d) growth hormone 31. Which of the following endocrine glands is unpaired? (a) Adrenal (b) Testes (c) Pituitary (d) Ovary 32. Junction between two neurons is called (a) cell junction (b) neuro muscular junction (c) neural joint (d) synapse 33. In humans, the life processes are controlled and regulated by (a) reproductive and endocrine systems (b) respiratory and nervous systems (c) endocrine and digestive systems (d) nervous and endocrine systems Short Answer Q uestions 34. Label the parts (a), (b), (c) and (d) and show the direction of flow of electrical signals in Figure 7.2. Fig. 7.2 62 EXE M PLAR P RO B LE M S – SCIENCE

35. Name the plant hormones responsible for the following (a) elongation of cells (b) growth of stem (c) promotion of cell division (d) falling of senescent leaves. 36. Label the endocrine glands in Figure 7.3. 37. In Figure 7.4 (a), (b) and (c), which appears more accurate and why? Fig. 7.3 Fig. 7.4 38. Label the parts of a neuron in Figure 7.5. Fig. 7.5 39. Match the terms of Column (A) with those of Column (B) Column (A) Column (B) (a) Olfactory receptors (i) Tongue (b) Thermo receptors (temperature receptors) (ii) Eye (c) Gustatoreceptors (iii) Nose (d) Photoreceptors (iv) Skin 40. What is a tropic movement? Explain with an example. 41. What will happen if intake of iodine in our diet is low? 42. What happens at the synapse between two neurons? CONTROL AND CO - ORDINATION 63

43. Answer the following : (a) Which hormone is responsible for the changes noticed in females at puberty? (b) Dwarfism results due to deficiency of which hormone? (c) Blood sugar level rises due to deficiency of which hormone? (d) Iodine is necessary for the synthesis of which hormone? 44. Answer the following : (a) Name the endocrine gland associated with brain? (b) Which gland secretes digestive enzymes as well as hormones? (c) Name the endocrine gland associated with kidneys? (d) Which endocrine gland is present in males but not in females? Long Answer Q uestions 45. Draw the structure of a neuron and explain its function. 46. What are the major parts of the brain? Mention the functions of different parts. 47. What constitutes the central and peripheral nervous systems? How are the components of central nervous system protected? 48. Mention one function for each of these hormones : (a) Thyroxin (b) Insulin (c) Adrenaline (d) Growth hormone (e) Testosterone. 49. Name various plant hormones. Also give their physiological effects on plant growth and development. 50. What are reflex actions? Give two examples. Explain a reflex arc. 51. “Nervous and hormonal systems together perform the function of control and coordination in human beings.” Justify the statement. 52. How does chemical coordination take place in animals? 53. Why is the flow of signals in a synapse from axonal end of one neuron to dendritic end of another neuron but not the reverse? 64 EXE M PLAR P RO B LE M S – SCIENCE

8CHAPTER How do Organisms Reproduce? Multiple Choice Q uestions 1. In the list of organisms given below, those that reproduce by the asexual method are (i) banana (b) (i), (iii) and (iv) (ii) dog (d) (ii), (iii) and (iv) (iii) yeast (iv) Amoeba (a) (ii) and (iv) (c) (i) and (iv) 2. In a flower, the parts that produce male and female gametes (germ cells) are (a) stamen and anther (b) filament and stigma (c) anther and ovary (d) stamen and style 3. Which of the following is the correct sequence of events of sexual reproduction in a flower? (a) pollination, fertilisation, seedling, embryo (b) seedling, embryo, fertilisation, pollination (c) pollination, fertilisation, embryo, seedling (d) embryo, seedling, pollination, fertilisation 4. Offspring formed by asexual method of reproduction have greater similarity among themselves because (i) asexual reproduction involves only one parent (ii) asexual reproduction does not involve gametes (iii) asexual reproduction occurs before sexual reproduction (iv) asexual reproduction occurs after sexual reproduction (a) (i) and (ii) (b) (i) and (iii) (c) (ii) and (iv) (d) (iii) and (iv)

5. Characters transmitted from parents to offspring are present in (a) cytoplasm (b) ribosome (c) golgi bodies (d) genes 6. Characters that are transmitted from parents to offspring during reproduction show (a) only similarities with parents (b) only variations with parents (c) both similarities and variations with parents (d) neither similarities nor variations 7. A feature of reproduction that is common to Amoeba, Spirogyra and Yeast is that (a) they reproduce asexually (b) they are all unicellular (c) they reproduce only sexually (d) they are all multicellular 8. In Spirogyra, asexual reproduction takes place by (a) breaking up of filaments into smaller bits (b) division of a cell into two cells (c) division of a cell into many cells (d) formation of young cells from older cells. 9. The ability of a cell to divide into several cells during reproduction in Plasmodium is called (a) budding (b) reduction division (c) binary fission (d) multiple fission 10. The correct sequence of reproductive stages seen in flowering plants is (a) gametes, zygote, embryo, seedling (b) zygote, gametes, embryo, seedling (c) seedling, embryo, zygote, gametes (d) gametes, embryo, zygote, seedling 11. The number of chromosomes in parents and offsprings of a particular species remains constant due to (a) doubling of chromosomes after zygote formation (b) halving of chromosomes during gamete formation (c) doubling of chromosomes after gamete formation (d) halving of chromosomes after gamete formation 66 EXE M PLAR P RO B LE M S – SCIENCE

12. In Rhizopus, tubular thread-like structures bearing sporangia at their tips are called (a) filaments (b) hyphae (c) rhizoids (d) roots 13. Vegetative propagation refers to formation of new plants from (a) stem, roots and flowers (b) stem, roots and leaves (c) stem, flowers and fruits (d) stem, leaves and flowers 14. Factors responsible for the rapid spread of bread mould on slices of bread are (i) large number of spores (ii) availability of moisture and nutrients in bread (iii) presence of tubular branched hyphae (iv) formation of round shaped sporangia (a) (i) and (iii) (b) (ii) and iv) (c) (i) and (ii) (d) (iii) and (iv) 15. Length of pollen tube depends on the distance between (a) pollen grain and upper surface of stigma (b) pollen grain on upper surface of stigma and ovule (c) pollen grain in anther and upper surface of stigma (d) upper surface of stigma and lower part of style 16. Which of the following statements are true for flowers? (i) Flowers are always bisexual (ii) They are the sexual reproductive organs (iii) They are produced in all groups of plants (iv) After fertilisation they give rise to fruits (a) (i) and (iv) (b) (ii) and (iii) (c) (i) and (iii) (d) (ii) and (iv) 17. Which among the following statements are true for unisexual flowers? (i) They possess both stamen and pistil (ii) They possess either stamen or pistil (iii) They exhibit cross pollination (iv) Unisexual flowers possessing only stamens cannot produce fruits (a) (i) and (iv) (b) (ii), (iii) and (iv) (c) (iii) and (iv) (d) (i), (iii) and (iv) HOW DO ORGANISMS REPRODUCE? 67

18. Which among the following statements are true for sexual reproduction in flowering plants? (i) It requires two types of gametes (ii) Fertilisation is a compulsory event (iii) It always results in formation of zygote (iv) Offspring formed are clones (a) (i) and (iv) (b) (i), (ii) and (iv) (c) (i), (ii) and (iii) (d) (i), (ii) and (iv) Fig. 8.1 19. In Figure 8.1, the parts A, B and C are sequentially (a) cotyledon, plumule and radicle (b) plumule, radicle and cotyledon (c) plumule, cotyledon and radicle (d) radicle, cotyledon and plumule 20. Offspring formed as a result of sexual reproduction exhibit more variations because (a) sexual reproduction is a lengthy process (b) genetic material comes from two parents of the same species (c) genetic material comes from two parents of different species (d) genetic material comes from many parents 21. Reproduction is essential for living organisms in order to (a) keep the individual organism alive (b) fulfill their energy requirement (c) maintain growth (d) continue the species generation after generation 22. During adolescence, several changes occur in the human body. Mark one change associated with sexual maturation in boys (a) loss of milk teeth (b) increase in height (c) cracking of voice (d) weight gain 23. In human females, an event that reflects onset of reproductive phase is (a) growth of body (b) changes in hair pattern (c) change in voice (d) menstruation 68 EXE M PLAR P RO B LE M S – SCIENCE

24. In human males, the testes lie in the scrotum, because it helps in the (a) process of mating (b) formation of sperm (c) easy transfer of gametes (d) all the above 25. Which among the following is not the function of testes at puberty? (i) formation of germ cells (ii) secretion of testosterone (iii) development of placenta (iv) secretion of estrogen (a) (i) and (ii) (b) (ii) and (iii) (c) (iii) and (iv) (d) (i) and (iv) 26. The correct sequence of organs in the male reproductive system for transport of sperms is ✂ ✂(a) testis vasdeferens urethra ✂ ✂(b) testis ureter urethra ✂ ✂(c) testis urethra ureter ✂ ✂(d) testis vasdeferens ureter 27. Which among the following diseases is not sexually transmitted? (a) Syphillis (b) Hepatitis (c) HIV - AIDS (d) Gonorrhoea Short Answer Q uestions 28. In a bisexual flower inspite of the young stamens being removed artificially, the flower produces fruit. Provide a suitable explanation for the above situation. 29. Can you consider cell division as a type of reproduction in unicellular organism? Give one reason. 30. What is a clone? Why do offsprings formed by asexual reproduction exhibit remarkable similarity? 31. Explain how, offspring and parents of organisms reproducing sexually have the same number of chromosomes? 32. Colonies of yeast fail to multiply in water, but multiply in sugar solution. Give one reason for this. HOW DO ORGANISMS REPRODUCE? 69

33. Why does bread mould grow profusely on a moist slice of bread rather than on a dry slice of bread? 34. Give two reasons for the appearance of variations among the progeny formed by sexual reproduction. 35. Would a Planaria cut vertically into two halves regenerate into two individuals? Complete Figure 8.2 D and E by indicating the regenerated regions. Fig. 8.2 36. From the internet, gather information about the chromosome numbers of five animals and five plants. Correlate the number with the size of organism and answer the following questions. (a) Do larger organisms have more number of chromosomes/cells? (b) Can organism with fewer chromosomes reproduce more easily than organisms with more number of chromosomes? (c) More the number of chromosomes/cells greater is the DNA content. Justify. 37. In tobacco plant, the male gametes have twenty four chromosomes. What is the number of chromosomes in the female gamete? What is the number of chromosomes in the zygote? 38. Why cannot fertilisation take place in flowers if pollination does not occur? 39. Is the chromosome number of zygote, embryonal cells and adult of a particular organism always constant? How is the constancy maintained in these three stages? 40. Where is the zygote located in the flower after fertilization? 41. Reproduction is linked to stability of population of a species. Justify the statement. 42. How are general growth and sexual maturation different from each other? 43. Trace the path of sperm during ejaculation and mention the gland and their functions associated with the male reproductive system. 70 EXE M PLAR P RO B LE M S – SCIENCE

44. What changes are observed in the uterus if fertilisation does not 71 occur? 45. W hat changes are observed in the u teru s su bsequ ent to implantation of young embryo? 46. What are the benefits of using mechanical barriers during sexual act? 47. In the given Figure 8.3 label the parts and mention their functions (a) Production of egg (b) Site of fertilisation (c) Site of implantation (d) Entry of the sperms Fig. 8.3 48. What would be the ratio of chromosome number between an egg and its zygote? How is the sperm genetically different from the egg? Long Answer Q uestions 49. Why are budding, fragmentation and regeneration all considered as asexual types of reproduction? With neat diagrams explain the process of regeneration in Planaria. 50. Write two points of difference between asexual and sexual types of reproduction. Describe why variations are observed in the offspring formed by sexual reproduction. 51. Distinguish between pollination and fertilisation. Mention the site and product of fertilisation in a flower. Draw a neat, labelled diagram of a pistil showing pollen tube growth and its entry into the ovule. 52. Distinguish between a gamete and zygote. Explain their roles in sexual reproduction. 53. Draw the diagram of a flower and label the four whorls. Write the names of gamete producing organs in the flower. HOW DO ORGANISMS REPRODUCE?

54. What is placenta? Mention its role during pregnancy? 55. What are various ways to avoid pregnancy? Elaborate any one method. 56. How does fertilisation take place? Fertilisation occurs once in a month. Comment. 57. Reproduction is essentially a phenomenon that is not for survival of an individual but for the stability of a species. Justify. 58. Describe sexually transmitted diseases and mention the ways to prevent them.     72 EXE M PLAR P RO B LE M S – SCIENCE

9CHAPTER Heredity and Evolution Multiple Choice Q uestions 1. Exchange of genetic material takes place in (a) vegetative reproduction (b) asexual reproduction (c) sexual reproduction (d) budding 2. Two pink coloured flowers on crossing resulted in 1 red, 2 pink and 1 white flower progeny. The nature of the cross will be (a) double fertilisation (b) self pollination (c) cross fertilisation (d) no fertilisation 3. A cross between a tall plant (TT) and short pea plant (tt) resulted in progeny that were all tall plants because (a) tallness is the dominant trait (b) shortness is the dominant trait (c) tallness is the recessive trait (d) height of pea plant is not governed by gene ‘T’ or ‘t’ 4. Which of the following statement is incorrect? (a) For every hormone there is a gene. (b) For every protein there is a gene. (c) For production of every enzyme there is a gene. (d) For every molecule of fat there is a gene 5. If a round, green seeded pea plant (RR yy) is crossed with wrinkled, yellow seeded pea plant, (rr YY) the seeds produced in F1 generation are (a) round and yellow (b) round and green (c) wrinkled and green (d) wrinkled and yellow

6. In human males all the chromosomes are paired perfectly except one. This/these unpaired chromosome is/are (i) large chromosome (ii) small chromosome (iii) Y-chromosome (iv) X-chromosome (a) (i) and (ii) (b) (iii) only (c) (iii) and (iv) (d) (ii) and (iv) 7. The maleness of a child is determined by (a) the X chromosome in the zygote (b) the Y chromosome in zygote (c) the cytoplasm of germ cell which determines the sex (d) sex is determined by chance 8. A zygote which has an X-chromosome inherited from the father will develop into a (a) boy (b) girl (c) X- chromosome does not determine the sex of a child (d) either boy or girl 9. Select the incorrect statement (a) Frequency of certain genes in a population change over several generations resulting in evolution (b) Reduction in weight of the organism due to starvation is genetically controlled (c) Low weight parents can have heavy weight progeny (d) Traits which are not inherited over generations do not cause evolution 10. New species may be formed if (i) DNA undergoes significant changes in germ cells (ii) chromosome number changes in the gamete (iii) there is no change in the genetic material (iv) mating does not take place (a) (i) and (ii) (b) (i) and (iii) (c) (ii), (iii) and (iv) (d) (i), (ii) and (iii) 11. Two pea plants one with round green seeds (RRyy) and another with wrinkled yellow (rrYY) seeds produce F progeny that have 1 round, yellow (RrYy) seeds. When F plants are selfed, the F 12 progeny will have new combination of characters. Choose the new combination from the following 74 EXE M PLAR P RO B LE M S – SCIENCE

(i) Round, yellow (b) (i) and (iv) (ii) Round, green (d) (i) and (iii) (iii) Wrinkled, yellow (iv) Wrinkled, green (a) (i) and (ii) (c) (ii) and (iii) 12. A basket of vegetables contains carrot, potato, radish and tomato. Which of them represent the correct homologous structures? (a) Carrot and potato (b) Carrot and tomato (c) Radish and carrot (d) Radish and potato 13. Select the correct statement (a) Tendril of a pea plant and phylloclade of O puntia are homologous (b) Tendril of a pea plant and phylloclade ofOpuntia are analogous (c) Wings of birds and limbs of lizards are analogous (d) Wings of birds and wings of bat are homologous 14. If the fossil of an organism is found in the deeper layers of earth, then we can predict that (a) the extinction of organism has occurred recently (b) the extinction of organism has occurred thousands of years ago (c) the fossil position in the layers of earth is not related to its time of extinction (d) time of extinction cannot be determined 15. Which of the following statements is not true with respect to variation? (a) All variations in a species have equal chance of survival (b) Change in genetic composition results in variation (c) Selection of variants by environmental factors forms the basis of evolutionary processes. (d) Variation is minimum in asexual reproduction 16. A trait in an organism is influenced by (a) paternal DNA only (b) maternal DNA only (c) both maternal and paternal DNA (d) neither by paternal nor by maternal DNA HEREDITY AND EVOLUTION 75

17. Select the group which shares maximum number of common characters (a) two individuals of a species (b) two species of a genus (c) two genera of a family (d) two genera of two families 18. According to the evolutionary theory, formation of a new species is generally due to (a) sudden creation by nature (b) accumulation of variations over several generations (c) clones formed during asexual reproduction (d) movement of individuals from one habitat to another 19. From the list given below, select the character which can be acquired but not inherited (a) colour of eye (b) colour of skin (c) size of body (d) nature of hair 20. The two versions of a trait (character) which are brought in by the male and female gametes are situated on (a) copies of the same chromosome (b) two different chromosomes (c) sex chromosomes (d) any chromosome 21. Select the statements that describe characteristics of genes (i) genes are specific sequence of bases in a DNA molecule (ii) a gene does not code for proteins (iii) in individuals of a given species, a specific gene is located on a particular chromosome (iv) each chromosome has only one gene (a) (i) and (ii) (b) (i) and (iii) (c) (i) and (iv) (d) (ii) and (iv) 22. In peas, a pure tall plant (TT) is crossed with a short plant (tt). The ratio of pure tall plants to short plants in F is 2 (a) 1 : 3 (b) 3 : 1 (c) 1 : 1 (d) 2 : 1 76 EXE M PLAR P RO B LE M S – SCIENCE

23. The number of pair (s) of sex chromosomes in the zygote of humans is (a) one (b) two (c) three (d) four 24. The theory of evolution of species by natural selection was given by (a) Mendel (b) Darwin (c) Morgan (d) Lamarck 25. Some dinosaurs had feathers although they could not fly but birds have feathers that help them to fly. In the context of evolution this means that (a) reptiles have evolved from birds (b) there is no evolutionary connection between reptiles and birds (c) feathers are homologous structures in both the organisms (d) birds have evolved from reptiles Short Answer Q uestions 26. How is the sex of a newborn determined in humans? 27. Do genetic combination of mothers play a significant role in determining the sex of a new born? 28. Mention three important features of fossils which help in the study of evolution. 29. Why do all the gametes formed in human females have an X chromosome? 30. In human beings, the statistical probability of getting either a male or female child is 50 : 50. Give a suitable explanation. 31. A very small population of a species faces a greater threat of extinction than a larger population. Provide a suitable genetic explanation. 32. What are homologous structures? Give an example. Is it necessary that homologous structures always have a common ancestor? 33. Does the occurrence of diversity of animals on earth suggest their diverse ancestry also? Discuss this point in the light of evolution. 34. Give the pair of contrasting traits of the following characters in pea plant and mention which is dominant and recessive (i) yellow seed (ii) round seed 35. Why did Mendel choose pea plant for his experiments? HEREDITY AND EVOLUTION 77

36. A woman has only daughters. Analyse the situation genetically and provide a suitable explanation. Long Answer Q uestions 37. Does geographical isolation of individuals of a species lead to formation of a new species? Provide a suitable explanation. 38. Bacteria have a simpler body plan when compared with human beings. Does it mean that human beings are more evolved than bacteria? Provide a suitable explanation. 39. All the human races like Africans, Asians, Europeans, Americans and others might have evolved from a common ancestor. Provide a few evidences in support of this view. 40. Differentiate between inherited and acquired characters. Give one example for each type. 41. Give reasons why acquired characters are not inherited. 42. Evolution has exhibited a greater stability of molecular structure when compared with morphological structures. Comment on the statement and justify your opinion. 43. In the following crosses write the characteristics of the progeny Cross Progeny (a) RR YY x RR YY ........................... Round, yellow Round, yellow ........................... ........................... (b) Rr Yy x Rr Yy ........................... Round, yellow Round, yellow ........................... ........................... (c) rr yy x rr yy ........................... wrinkled, green wrinkled, green ........................... (d) RR YY x rr yy Round, yellow wrinkled green 44. Study the following cross and showing self pollination in F1, fill in the blank and answer the question that follows Parents RRYY x rryy Round, yellow wrinkled, green F— Rr Yy x ? 1 Round, yellow 45. In question 44, what are the combinations of character in the F 2 progeny? What are their ratios? 46. Give the basic features of the mechanism of inheritance. 47. Give reasons for the appearance of new combinations of characters in the F2 progeny. 78 EXE M PLAR P RO B LE M S – SCIENCE

1 0CHAPTER Light – Reflection and Refraction Multiple Choice Q uestions 1. Which of the following can make a parallel beam of light when light from a point source is incident on it? (a) Concave mirror as well as convex lens (b) Convex mirror as well as concave lens (c) Two plane mirrors placed at 90° to each other (d) Concave mirror as well as concave lens 2. A 10 mm long awl pin is placed vertically in front of a concave mirror. A 5 mm long image of the awl pin is formed at 30 cm in front of the mirror. The focal length of this mirror is (a) – 30 cm (b) – 20 cm (c) – 40 cm (d) – 60 cm 3. Under which of the following conditions a concave mirror can form an image larger than the actual object? (a) When the object is kept at a distance equal to its radius of curvature (b) When object is kept at a distance less than its focal length (c) When object is placed between the focus and centre of curvature (d) When object is kept at a distance greater than its radius of curvature 4. Figure 10.1 shows a ray of light as it travels from medium A to medium B. Refractive index of the medium B relative to medium A is (a) ✸   ✷ Fig. 10.1 (b) ✁ ✂ ✄ (c) ✶✂ ✁ (d) ☎

Fig. 10.2 5. A light ray enters from medium A to medium B as shown in Figure 10.2. The refractive index of medium B relative to A will be (a) greater than unity (b) less than unity (c) equal to unity (d) zero 6. Beams of light are incident through the holes A and B and emerge out of box through the holes C and D respectively as shown in the Figure10.3. Which of the following could be inside the box? (a) A rectangular glass slab (b) A convex lens (c) A concave lens (d) A prism Fig. 10.3 7. A beam of light is incident through the holes on side A and emerges out of the holes on the other face of the box as shown in the Figure 10.4. Which of the following could be inside the box? (a) Concave lens (b) Rectangular glass slab (c) Prism (d) Convex lens Fig. 10.4 8. Which of the following statements is true? (a) A convex lens has 4 dioptre power having a focal length 0.25 m (b) A convex lens has –4 dioptre power having a focal length 0.25 m (c) A concave lens has 4 dioptre power having a focal length 0.25 m (d) A concave lens has –4 dioptre power having a focal length 0.25 m 80 EXE M PLAR P RO B LE M S – SCIENCE

9. Magnification produced by a rear view mirror fitted in vehicles (a) is less than one (b) is more than one (c) is equal to one (d) can be more than or less than one depending upon the position of the object in front of it 10. Rays from Sun converge at a point 15 cm in front of a concave mirror. Where should an object be placed so that size of its image is equal to the size of the object? (a) 15 cm in front of the mirror (b) 30 cm in front of the mirror (c) between 15 cm and 30 cm in front of the mirror (d) more than 30 cm in front of the mirror 11. A full length image of a distant tall building can definitely be seen by using (a) a concave mirror (b) a convex mirror (c) a plane mirror (d) both concave as well as plane mirror 12. In torches, search lights and headlights of vehicles the bulb is placed (a) between the pole and the focus of the reflector (b) very near to the focus of the reflector (c) between the focus and centre of curvature of the reflector (d) at the centre of curvature of the reflector 13. The laws of reflection hold good for Fig. 10.5 (a) plane mirror only (b) concave mirror only (c) convex mirror only (d) all mirrors irrespective of their shape 14. The path of a ray of light coming from air passing through a rectangular glass slab traced by four students are shown as A, B, C and D in Figure 10.5. Which one of them is correct? (a) A (b) B (c) C (d) D LIGHT – REFLECTION AND REFRACTION 81

15. You are given water, mustard oil, glycerine and kerosene. In which of these media a ray of light incident obliquely at same angle would bend the most? (a) Kerosene (b) Water (c) Mustard oil (d) Glycerine 16. Which of the following ray diagrams is correct for the ray of light incident on a concave mirror as shown in Figure 10.6? Fig. 10.6 Fig. A Fig. B Fig. C Fig. D (a) Fig. A (b) Fig. B (c) Fig. C (d) Fig. D 17. Which of the following ray diagrams is correct for the ray of light incident on a lens shown in Fig. 10.7? Fig. 10.7 Fig. A Fig. B Fig. D Fig. C (a) Fig. A. 82 (b) Fig. B. (c) Fig. C. (d) Fig. D. EXE M PLAR P RO B LE M S – SCIENCE

18. A child is standing in front of a magic mirror. She finds the image 83 of her head bigger, the middle portion of her body of the same size and that of the legs smaller. The following is the order of combinations for the magic mirror from the top. (a) Plane, convex and concave (b) Convex, concave and plane (c) Concave, plane and convex (d) Convex, plane and concave 19. In which of the following, the image of an object placed at infinity will be highly diminished and point sized? (a) Concave mirror only (b) Convex mirror only (c) Convex lens only (d) Concave mirror, convex mirror, concave lens and convex lens Short Answer Q uestions 20. Identify the device used as a spherical mirror or lens in following cases, when the image formed is virtual and erect in each case. (a) Object is placed between device and its focus, image formed is enlarged and behind it. (b) Object is placed between the focus and device, image formed is enlarged and on the same side as that of the object. (c) Object is placed between infinity and device, image formed is diminished and between focus and optical centre on the same side as that of the object. (d) Object is placed between infinity and device, image formed is diminished and between pole and focus, behind it. 21. Why does a light ray incident on a rectangular glass slab immersed in any medium emerges parallel to itself? Explain using a diagram. 22. A pencil when dipped in water in a glass tumbler appears to be bent at the interface of air and water. Will the pencil appear to be bent to the same extent, if instead of water we use liquids like, kerosene or turpentine. Support your answer with reason. 23. How is the refractive index of a medium related to the speed of light? Obtain an expression for refractive index of a medium with respect to another in terms of speed of light in these two media? 24. Refractive index of diamond with respect to glass is 1.6 and absolute refractive index of glass is 1.5. Find out the absolute refractive index of diamond. LIGHT – REFLECTION AND REFRACTION

25. A convex lens of focal length 20 cm can produce a magnified virtual as well as real image. Is this a correct statement? If yes, where shall the object be placed in each case for obtaining these images? 26. Sudha finds out that the sharp image of the window pane of her science laboratory is formed at a distance of 15 cm from the lens. She now tries to focus the building visible to her outside the window instead of the window pane without disturbing the lens. In which direction will she move the screen to obtain a sharp image of the building? What is the approximate focal length of this lens? 27. How are power and focal length of a lens related? You are provided with two lenses of focal length 20 cm and 40 cm respectively. Which lens will you use to obtain more convergent light? 28. Under what condition in an arrangement of two plane mirrors, incident ray and reflected ray will always be parallel to each other, whatever may be angle of incidence. Show the same with the help of diagram. 29. Draw a ray diagram showing the path of rays of light when it enters with oblique incidence (i) from air into water; (ii) from water into air. Long Answer Q uestions 30. Draw ray diagrams showing the image formation by a concave mirror when an object is placed (a) between pole and focus of the mirror (b) between focus and centre of curvature of the mirror (c) at centre of curvature of the mirror (d) a little beyond centre of curvature of the mirror (e) at infinity 31. Draw ray diagrams showing the image formation by a convex lens when an object is placed (a) between optical centre and focus of the lens (b) between focus and twice the focal length of the lens (c) at twice the focal length of the lens (d) at infinity (e) at the focus of the lens 32. Write laws of refraction. Explain the same with the help of ray diagram, when a ray of light passes through a rectangular glass slab. 84 EXE M PLAR P RO B LE M S – SCIENCE

33. Draw ray diagrams showing the image formation by a concave lens when an object is placed (a) at the focus of the lens (b) between focus and twice the focal length of the lens (c) beyond twice the focal length of the lens 34. Draw ray diagrams showing the image formation by a convex mirror when an object is placed (a) at infinity (b) at finite distance from the mirror 35. The image of a candle flame formed by a lens is obtained on a screen placed on the other side of the lens. If the image is three times the size of the flame and the distance between lens and image is 80 cm, at what distance should the candle be placed from the lens? What is the nature of the image at a distance of 80 cm and the lens? 36. Size of image of an object by a mirror having a focal length of 20 cm is observed to be reduced to 1/3rd of its size. At what distance the object has been placed from the mirror? What is the nature of the image and the mirror? 37. Define power of a lens. What is its unit? One student uses a lens of focal length 50 cm and another of –50 cm. What is the nature of the lens and its power used by each of them? 38. A student focussed the image of a candle flame on a white screen using a convex lens. He noted down the position of the candle screen and the lens as under Position of candle = 12.0 cm Position of convex lens = 50.0 cm Position of the screen = 88.0 cm (i) What is the focal length of the convex lens? (ii) Where will the image be formed if he shifts the candle towards the lens at a position of 31.0 cm? (iii) What will be the nature of the image formed if he further shifts the candle towards the lens? (iv) Draw a ray diagram to show the formation of the image in case (iii) as said above. LIGHT – REFLECTION AND REFRACTION 85

1 1CHAPTER The Human Eye and the Colourful World Multiple Choice Q uestions 1. A person cannot see distinctly objects kept beyond 2 m. This defect can be corrected by using a lens of power (a) + 0.5 D (b) – 0.5 D (c) + 0.2 D (d) – 0.2 D 2. A student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his text book. Which of the following statements is correct? (a) The near point of his eyes has receded away (b) The near point of his eyes has come closer to him (c) The far point of his eyes has come closer to him (d) The far point of his eyes has receded away 3. A prism ABC (with BC as base) is placed in different orientations. A narrow beam of white light is incident on the prism as shown in Figure 11.1. In which of the following cases, after dispersion, the third colour from the top corresponds to the colour of the sky? (a) (i) (b) (ii) (c) (iii) (d) (iv) Fig.11.1

4. At noon the sun appears white as 87 (a) light is least scattered (b) all the colours of the white light are scattered away (c) blue colour is scattered the most (d) red colour is scattered the most 5. Which of the following phenomena of light are involved in the formation of a rainbow? (a) Reflection, refraction and dispersion (b) Refraction, dispersion and total internal reflection (c) Refraction, dispersion and internal reflection (d) Dispersion, scattering and total internal reflection 6. Twinkling of stars is due to atmospheric (a) dispersion of light by water droplets (b) refraction of light by different layers of varying refractive indices (c) scattering of light by dust particles (d) internal reflection of light by clouds 7. The clear sky appears blue because (a) blue light gets absorbed in the atmosphere (b) ultraviolet radiations are absorbed in the atmosphere (c) violet and blue lights get scattered more than lights of all other colours by the atmosphere (d) light of all other colours is scattered more than the violet and blue colour lights by the atmosphere 8. W hich of the following statements is correct regarding the propagation of light of different colours of white light in air? (a) Red light moves fastest (b) Blue light moves faster than green light (c) All the colours of the white light move with the same speed (d) Yellow light moves with the mean speed as that of the red and the violet light 9. The danger signals installed at the top of tall buildings are red in colour. These can be easily seen from a distance because among all other colours, the red light (a) is scattered the most by smoke or fog (b) is scattered the least by smoke or fog (c) is absorbed the most by smoke or fog (d) moves fastest in air HUMAN EYE AND THE COLOURFUL WORLD